1. Field of the Invention
The present invention relates to a next generation mobile communication, and more particularly, to a method for controlling a data flow in a communication system.
2. Discussion of the Related Art
Generally, a sliding-window data flow control is widely used when transmitting packets in a communication system in order to prevent losses of the packets and for many other purposes. Particularly, the sliding-window data flow control in a radio link control (hereinafter, xe2x80x9cRLCxe2x80x9d) layer has its window size being in the range of 0 to 212xe2x88x921, and each packet having its sequence number within the range of the window size is transmitted to a receiving system.
FIG. 1 illustrates a typical sliding-window data flow control procedure in a communication system according to the prior art. According to the FIG. 1, a receiving system in the RLC layer initially sends a window size number (hereinafter, xe2x80x9cWSNxe2x80x9d), which limits the number of protocol data units (hereinafter, xe2x80x9cPDUxe2x80x9d) subjected to be transmitted, to an originating system (S9). Then the originating system generates a corresponding number of PDUs based on the window size number received and transmits them to the receiving system (S10, S11). However, when a severe congestion occurs due to overloads in the system resources and the limited capacity of the system environment, the receiving system sets the WSN equal to 0 and transmits it back to the originating system (S12) After the originating system suspects that the congestion has occurred in the receiving system by receiving the WSN set to 0, it resets Tx_window_size to 0 and stops transmitting the PDUs. When the originating system receives the WSN greater than 0 from the receiving system after the congestion is terminated (S13), it resets the Tx_window_size based on the WSN received and begins to transmit the corresponding PDUs again. However, if the WSN is lost or not reached to the originating system for some reason, the originating and receiving systems will be in at total deadlock situations. In other words, the receiving system keeps waiting to receive the PDUs corresponding to the lost WSN the receiving system has sent, and the originating system still does not transmit any PDUs since the value of the Tx_window_size is still equal to 0. Consequently, said deadlock situations result ineffective uses of the system resources and unnecessary delays.
Accordingly, the present invention is directed to a method for controlling a data flow that obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method for controlling a data flow in a communication system that eliminates or breaks the deadlock situations in originating and receiving systems resulting from the loss of the WSN the receiving system has sent to the originating system.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a method of controlling a data flow in a communication system includes transmitting a window size number equal to 0 from said receiving system to said originating system in order to stop transmitting protocol data units (PDU); transmitting a desired window size number greater than 0 from the receiving system to the originating system; retransmitting the window size number greater than 0 after a predetermined time period has elapsed since the last transmission of the desired window size number, said repeating being continuously performed until any one of corresponding PDUs is transmitted from the originating system to the receiving system; stopping said repeating and completing to transmit all of the corresponding PDUs if there is any one of the corresponding PDUs is transmitted from the originating system to the receiving system; and reporting an error to a higher layer and terminating a connection between the originating and receiving systems if there is no corresponding PDU transmitted to the receiving system until said retransmission is repeated a predetermined number of times.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.